The ability to make sense out of the actions of others is critical to people's daily functioning. Adults are social experts: They understand that people's actions are directed at goals and are driven by intentions. In this article, the authors highlight key findings from studies examining infants' understanding of human action. These findings suggest that infants come to understand that intentions and attention guide human action within the first few months of their lives. By 13 months, infants understand that intentions are specific to individuals, yet there are some actions that are shared by all individuals within a group. Taken together, the evidence suggests that infants are well on their way to becoming social experts by their second birthdays.